Here is the PolyEd How To Guide on making a level.
Basically I will put a few points in to get you started, and the rest is all butchered qspecs..  my thanks and appologies to Niklata, Oliver Montunay, and the others.

First, you need a texture wad.  Download quaketex.zip with the quake101.wad.  This wad will have every texture from Quake version 1.01.  Hopefully it will be included in any CD you find with PolyEd on it.

Second, get Qbsp, Light, & Vis stuff.  They will all be in a qbsp package...  try cdrom.com in the qbsp_pak_tools section.  Get the ones for registerd version, and get either the DOS or the windows ones.  Make sure they are for the registered version.

Make a map, f3 to save a map file, and then at a dos prompt do this:
qbsp mymap  {this will build it}
light mymap {this will put the proper light sources in the right places}
vis mymap {this will optomize kind of}

then copy the resulting bsp file to your id1/maps directory.  What?  you don't have a maps directory?  Well just make one.  Now go into quake, pull down the console and type: map mymap.  

cool, huh?

Notes on map making:
This is not like doom.  You arn't building sectors, you're putting walls together, walls that have thickness.  Think of it as big slabs.  And remember, 4 walls are not enough to make a room, You must not forget to put a cieling and a floor in.

The following specs will guide you in making those flickering lights and teleport devices and all the other cool stuff.

----------------------------------------
Quake MAP Specs


Last Updated: 8/22/96 8:52PM EST


Info on entities/maps and maintenance by Niklata (Nicholas Dwarkanath)

Coordinate System:

Quake uses a standard right-handed (X,Y,Z) coordinate system. If you're not familiar with the reference of "right-handed" to a coordinate system, it basically provides a tactile and visual discription of the mechanics of the system. If you point your fingers towards the positive x-axis and bend your fingers so that your knuckles face the positive y-axis, your thumb will point towards the positive z-axis:


        ^ z+
        |
        |
        |
        |
        |------------> y+
       /
      /
     /
    /
   <
 x+



Some entities also need to have an angle tag that tells the direction it is facing. The values possible are listed below:


0-359: Normal Angle (zero == east)
-1: Up
-2: Down



Brushes:

Brushes are one of the two primary components of a MAP file. Each brush defines a solid region. Brushes define this region as the intersection of four or more planes. Each plane is defined by three noncolinear points. These points must go in a clockwise orientation:


1--2----------------->
|
3
|
|
|
|
|
,


x_off     - Texture x-offset (must be multiple of 16)
y_off     - Texture y-offset (must be multiple of 16)
rot_angle - floating point value indicating texture rotation
x_scale   - scales x-dimension of texture (negative value to flip)
y_scale   - scales y-dimension of texture (negative value to flip)
Many entity/brush combinations can be put into a map file. All MAP files must contain with a worldspawn entity, usually as the first entry. This entry defines all of the normal brushes that make up the structure of the level. There should be only one worldspawn entity per MAP file. Here's the syntax of the worldspawn class:


"classname" "worldspawn" // Tells Quake to spawn the world
"wad" "DIRPATH"          // tells what graphics (texture) WAD2 file to use.
"message" "TITLE"        // The title of the level
"worldtype" "#"          // Describes time of environment (changes appearance/name of keys)
                         // 0 == Medieval (medieval)
                         // 1 == Runic (metal)
                         // 2 == Present (base)
"sounds" "#"             // Tells the CD player which track to play.
"light" "#"              // Default light level


Entities are the second major component of Quake MAP files. An entity is basically a bit like a thing, but they also function as triggers and as pathmarkers. 

"spawnflags" tag: 

General:

256  - Normal Skill or higher
512  - Hard Skill or higher
1792 - Appears in deathmatch only

item_health:
1    - Larger Health/Larger Ammo
2    - Megahealth

monster_zombie:
1    - Crucified Zombie



General Entity syntax:

Specifics    Args      Description
--------------------------------------------------------------------------------
"classname"  "name"    // Type of entity to be defined (mandatory)
"origin"     "X Y Z"   // Coordinates of where it starts in space.
"angle"      "#"       // Direction it faces or moves (sometimes in degrees)
"light"      "#"       // Used with the light classname.
"target"     "t#"      // Matches a targetname.
"targetname" "t#"      // Like a linedef tag.
"killtarget" "#"       // Removes target when triggered?
"spawnflags" "#"       // Used to flag/describe an entity that is not default.
"style"      "#"       // Used to flag/describe an entity that is not default.
"message"    "string"  // Message displayed when triggered (\n for linebreaks)
"mangle"     "X Y Z"   // Point where the intermission camera looks at

specifics/args present only in models:

"speed"      "#"       // How fast the model is moved.
"wait"       "#"       // How long a pause between completion of movement or
                       // return to original position (in seconds or 10ths)
"lip"        "#"       // Seems to be a means of adjusting the starting position.
"dmg"        "#"       // How much damage the model causes when it shuts on you?
"health"     "#"       // How much damage the model takes before it triggers
"delay"      "#"       // Time before event is triggered
"sounds"     "#"       // How much damage the model causes when it shuts on you?
"wad"        "wadfile" // The wad2 graphics file used by the world for textures.
"height"     "#"       // How high a platform will raise

All known entities (current for Shareware Quake 1.01):


air_bubbles                   : Rising bubbles

ambient_drip                  : Dripping sound
ambient_drone                 : Engine/machinery sound
ambient_comp_hum              : Computer background sounds
ambient_flouro_buzz           : Flourescent buzzing sound
ambient_light_buzz            : Buzzing sound from light
ambient_suck_wind             : Wind sound
ambient_swamp1                : Frogs croaking
ambient_swamp2                : Slightly different sounding frogs croaking
ambient_thunder               : Thunder sound

event_lightning               : Lightning (Used to kill Cthon, shareware boss)

func_door                     : Door
func_door_secret              : A door that is triggered to open
func_wall                     : A moving wall?
func_button                   : A button
func_train                    : A platform (moves along a "train")
func_plat                     : A lift/elevator
func_dm_only                  : A teleporter that only appears in deathmatch
func_illusionary              : Creates brush that appears solid, but isn't.

info_null                     : Used as a placeholder (removes itself)
info_notnull                  : Used as a placeholder (does not remove itself)
info_intermission             : Cameras positioning for intermission (?)
info_player_start             : Main player starting point (only one allowed)
info_player_deathmatch        : A deathmatch start (more than one allowed)
info_player_coop              : A coop player start (more than one allowed)
info_player_start2            : Return point from episode
info_teleport_destination     : Gives coords for a teleport destination using a targetname

All item_ tags may have a target tag.  It triggers 
the event when the item is picked up.

item_cells                    : Ammo for the Thunderbolt
item_rockets                  : Ammo for Rocket/Grenade Launcher
item_shells                   : Ammo for both Shotgun and SuperShotgun
item_spikes                   : Ammo for Perforator and Super Perforator
item_weapon                   : Generic weapon class
item_health                   : Medkit
item_artifact_envirosuit      : Environmental Protection Suit
item_artifact_super_damage    : Quad Damage
item_artifact_invulnerability : Pentagram of Protection
item_artifact_invisibility    : Ring of Shadows (Invisibility)
item_armorInv                 : Red armor
item_armor2                   : Yellow armor
item_armor1                   : Green armor
item_key1                     : Silver Key
item_key2                     : Gold Key
item_sigil                    : Sigil (a rune)

light                         : A projected light. No visible lightsource.
light_torch_small_walltorch   : Small wall torch (gives off light)
light_flame_large_yellow      : Large yellow fire (gives off light)
light_flame_small_yellow      : Small yellow fire (gives off light)
light_flame_small_white       : Small white fire  (gives off light)
light_fluoro                  : Fluorescent light? (Gives off light, humming sound?)
light_fluorospark             : Fluorescent light? (Gives off light, makes sparking sound)
light_globe                   : Light that appears as a globe sprite

monster_army                  : Grunt
monster_dog                   : Attack dog
monster_ogre                  : Ogre
monster_ogre_marksman         : Ogre (synonymous with monster_ogre)
monster_knight                : Knight
monster_zombie                : Zombie
monster_wizard                : Scragg (Wizard)
monster_demon1                : Fiend (Demon)
monster_shambler              : Shambler
monster_boss                  : Cthon (Boss of Shareware Quake)
monster_enforcer              : Enforcer
monster_hell_knight           : Hell Knight
monster_shalrath              : Shalrath
monster_tarbaby               : Slime
monster_fish                  : Fish
monster_oldone                : Shubb-Niggurath
                                       (requires a misc_teleportrain and a info_intermission)

misc_fireball                 : Small fireball (gives off light, harms player)
misc_explobox                 : Large Nuclear Container
misc_explobox2                : Small Nuclear Container
misc_teleporttrain            : Spiked ball needed to telefrag monster_oldone

path_corner                   : Used to define path of func_train platforms

trap_spikeshooter             : Shoots spikes (nails)
trap_shooter                  : Fires nails without needing to be triggered.

trigger_teleport              : Teleport (all trigger_ tags are triggered by walkover)
trigger_changelevel           : Changes to another level
trigger_setskill              : Changes skill level
trigger_counter               : Triggers action after it has been triggered count times.
trigger_once                  : Triggers action only once
trigger_multiple              : Triggers action (can be retriggered)
trigger_onlyregistered        : Triggers only if game is registered (registered == 1)
trigger_secret                : Triggers action and awards secret credit.
trigger_monsterjump           : Causes triggering monster to jump in a direction
trigger_relay                 : Allows delayed/multiple actions from one trigger 
trigger_push                  : Pushes a player in a direction (like a windtunnel)
trigger_hurt                  : Hurts whatever touches the trigger

weapon_supershotgun           : Super Shotgun
weapon_nailgun                : Perforator
weapon_supernailgun           : Super Perforator
weapon_grenadelauncher        : Grenade Launcher
weapon_rocketlauncher         : Rocket Launcher
weapon_lightning              : Lightning Gun




Entity 'class' examples


Lights

For all light-emmitting entities, spawnflags and style have special meanings:


Spawnflags:
0 - Light starts on.  Switches off when triggered.
1 - Light starts off.  Switches on when triggered.

Style:
0  - normal
1  - flicker (first variety)
2  - slow strong pulse
3  - candle (first variety)
4  - fast strobe
5  - gentle pulse
6  - flicker (second variety)
7  - candle (second variety)
8  - candle (third variety)
9  - slow strobe
10 - flourescent flicker
11 - slow pulse, not fading to black
   
   styles 32-62 are assigned by the light program for switchable lights

63 - testing


Regular Light:


    "classname" "light"
    "light" "#"         // Tells how bright the light is (optional - default 200)
    "style" "#"         // How the light appears
    "spawnflags" "#"    // State light starts in
    "targetname" "#"    // Target id of the light


Fluorescent Light:

    "classname" "light_fluoro"
    "light" "#"         // Tells how bright the light is (optional - default 200)
    "style" "#"         // How the light appears
    "spawnflags" "#"    // State light starts in
    "targetname" "#"    // Target id of the light

Fluorescent Light (makes sparking sound):
    "classname" "light_fluorospark"
    "light" "#"         // Tells how bright the light is (optional - default 200)
    "style" "#"         // How the light appears
    "spawnflags" "#"    // State light starts in
    "targetname" "#"    // Target id of the light

Torches:

    "classname" "light_torch_small_walltorch"
    "light" "#"         // Tells how bright the light is (optional - default 200)
    "style" "#"         // How the light appears
    "spawnflags" "#"    // State light starts in
    "targetname" "#"    // Target id of the light

Fire:

"classname" "light_flame_large_yellow, light_flame_small_yellow, light_flame_small_white"
"light" "#"         // Tells how bright the light is (optional)
"origin" "X Y Z"



Player Movement Entities


Level Change Trigger (attaches to brush):

    "classname" "trigger_changelevel"
    "map" "mapname"  // Map to change to on trigger (e.g. e1m8)
    "spawnflags" "#" // Flags describing the object (optional)

Teleport Trigger (attaches to brush):

    "classname" "trigger_teleport"
    "target" "t#"     // Teleport destination name to teleport to.
    "targetname" "t#" // Trigger name (optional) - only teleports once
                                             activated if targetname is present.
Teleport Destination:

    "classname" "info_teleport_destination"
    "angle" "#"       // angle the player will face upon leaving teleport
    "targetname" "t#" // Teleport's trigger name

 Movers


Door (attaches to brush):

    "classname" "func_door, func_door_secret"
    "angle" "#"      // angle it faces
    "speed" "#"      // speed of movement
    "targetname" "#" // Door's trigger name
    "sounds" "#"     // sound it makes
    "wait" "#"       // delay before closing
    "spawnflags "#"       // Flags describing the object (optional)
    "lip" "#"        // some kind of offset (optional)

Spawns on certain skill levels (controlled by spawnflags), can be removed by a trigger. (attaches to brush):

    "classname" "func_wall"
    "spawnflags" "#" // flags for something (optional I'd guess)

A platform (i.e. lift or elevator, attaches to brush):

    "classname" "func_plat"
    "height" "#" // height it rises? (optional)
    "sounds" "#" // sound it makes (optional)

Moving platform (Attaches to brush):

    "classname" "func_train"
    "sounds" "#"      // Sound it makes when activated
    "speed" "#"       // Speed at which it moves (optional)
    "target" "t#"     // Trigger name of its first path_corner destination
    "targetname" "t#" // Its trigger name
    "dmg" "#"         // Damage done on crush

Describes path of train/monsters:

    "classname" "path_corner"
    "origin" "X Y Z"
    "target" "t#"     // Trigger name of next train destination.
    "targetname" "t#" // It's trigger name.




Triggers/Switches


A button/switch (attaches to brush):

    "classname" "func_button"
    "angle" "#"   // Angle button moves?
    "speed" "#"   // Speed it moves in?
    "target" "t#" // Trigger name of target entity
    "health" "#"  // If there is health, button is shootable
    "sounds" "#"  // Sound it makes when activated
                                      // 1 == Steam Metal
                                      // 2 == Wooden Clunk
                                      // 3 == Metallic Click
                                      // 4 == In-Out
    "wait" "#"    // Wait until retrigger? (-1 stays pressed)
    "delay" "#"   // Delay before action is triggered

Walk-over trigger (attaches to brush):

    "classname" "trigger_once, trigger_multiple, trigger_onlyregistered, trigger_secret"
    "style" "#"       // 32 works
    "killtarget" "t#" // Kills something [for triggering monster events] (optional)
    "target" "t#"     // Trigger name of target
    "sounds" "#"      // Sound made when triggered
                                          // 1 == Secret Sound
                                          // 2 == Beep Beep
                                          // 3 == Large Switch
                                          // 4 == Set "message" to text string
    "wait" "#"        // Delay before retrigger. some classes only. (optional)
    "delay" "#"       // Delay before action is triggered


Triggers target after it is triggered count times:

    "classname" "trigger_counter" 
    "targetname" "t#" // Its trigger name
    "target" "t#"     // Trigger name of its target
    "count" "#"       // Decrements on each trigger.  When 0 activates target.
    "wait" "#"        // Required delay before retrigger
    "delay" "#"       // Delay before action is triggered

Used to stagger events on a trigger:

    "classname" "trigger_relay"
    "origin" "X Y Z"  // Where it is located
    "killtarget" "#"  // Removes targeted entity (optional)
    "targetname" "t#" // Its trigger name
    "target" "t#"     // Trigger name of its target
    "delay" "#"       // Delay before action is triggered

Makes a monster jump when it reaches a brush:

	"classname" "trigger_monsterjump"
    "speed" "#"       // Forward velocity of the monster jump
    "height" "#"      // How high the monster jumps
    "angle" "#"       // Angle towards which the monster jumps

An invisible brush?:

	"classname" "func_illusionary"




Traps/Things harmful to you:


Triggerable Nail-firing trap:

    "classname" "trap_spikeshooter"
    "angle" "#"       // Angle the trap fires at
    "targetname" "t#" // Trap's trigger name
    "spawnflags" "#"  // ??? 1024 works

Constant Nail-firing trap:


    "classname" "trap_shooter"
    "angle" "#"       // Angle the trap fires at
    "spawnflags" "#"  // ??? 1024 works
    "wait" "#"        // Time between shots

Fireballs:

    "classname" "misc_fireball"
    "speed" "#" // Tells how fast the fireball moves



Miscellaneous:



Pushes the player in a direction:

	"classname" "trigger_push"
    "speed" "#"       // Force of the push
	"angle" "#"       // Direction player is pushed towards (-1=up -2=down, other=normal)

Cameras for the intermission screen:


    "classname" "info_intermission"
    "mangle" "X Y Z" // location the camera looks at
    "angle" "#"      // angle of the camera

Setting difficulty level (attaches to brush):
    "classname" "trigger_setskill"
    "message" "#"   // Skill level to change to.


Lightning used to kill the boss of shareware.  I'll figure out how to use
it later...  I pretty much know how, I just want to test it before I
put it here :).  From the testing I've done, the lightning produced will
not damage a player, however.  It probably triggers a script to give the
boss character damage.

    "classname" "event_lightning"
    "origin" "X Y Z"  // location of lightning (origin?)
    "targetname" "t#" // It's trigger name




 Level Structures


 Moving Platforms:


Creating a moving platform isn't that difficult.   Here's an example:


"classname" "func_train"
"sounds" "1"
"speed" "128"
"target" "t1dest1"
"targetname" "t1"

(attach it to brush)

Now you define each of the path_corners it will travel to.  When it reaches
a path_corner, it will float to the next path_corner defined in the target
tag of the path_corner.  The platform will start at the path_corner pointed
to by the platform's target tag.  It will continue the loop indefinitely
and it will go through walls to get to its destination.  Here's its path_corners
would look like:

"classname" "path_corner"
"targetname" "t1dest1"
"target"" "t1dest2"

"classname" "path_corner"
"origin" "0 128 0"
"targetname" "t1dest2"
"target"" "t1dest1"

Monsters and Triggers:


Have you been wondering how you can get events to trigger when a monster dies, as first
seen in E1M2 with the demons?  Well, it's not too difficult.  When you attach a
target tag to a monster, the monster's death will trigger the event.  I believe
(not tested) that if other monsters have a targetname tag the same as a monster
with the target tag, the target event will only occur when all monsters with
a matching targetname tag are dead.  The monster with the target tag need not
have the targetname tag.



How to use trigger_count:

The trigger_count class is quite an interesting trigger. You know of the area in E1M1 where you have to hit the three switches to open the door? Well, that's done using a trigger_counter. Each of the buttons you hit has its target property set so it points to a trigger_counter. The trigger_counter has its count tag set to three. Each time a switch is hit, the trigger_counter's count property will decrement by one. When it reaches zero, it will open the door. Each button can only be triggered once as it has a wait of -1. Here's an example given to me by Remco Stoffer:


 "classname"	"func_door"
 "targetname"    "door2"
 "target"        "light1"
 "angle"	"-1"
 "wait" "-1"
 "sounds" "4"
 "message"   "press all buttons"

 "classname"      "trigger_counter"
 "count"          "3"
 "targetname"     "door1"
 "target"         "door2"
 "wait"           "-1"

 "classname"      "func_button"
 "angle"          "0"
 "wait"           "-1"
 "target"         "door1"

 "classname"      "func_button"
 "angle"          "0"
 "wait"           "-1"
 "target"         "door1"

 "classname"      "func_button"
 "angle"          "0"
 "wait"           "-1"
 "target"         "door1"


Teleporting Monsters:

Unlike in Doom-Engine games, you can precisely teleport monsters into new locations in Quake. To do so, you must first create a out of reach area for the monsters to reside in. Give this area a trigger_teleport tag and assign a targetname tag to it. Create a teleport_destination where you want the monster to appear. Now, you must create a trigger whose target property points to the trigger_teleport's targetname. When this trigger is activated, the monster in the room will teleport to the teleport_destination. Make sure that there is only one monster per room and one room per teleport_destination. Otherwise, when the teleport is triggered, all the monsters will telefrag each other (like what happens in E1M7 when you win).

Properties of Buttons:

The behavior of buttons can be altered in many ways. By default, buttons are activated by pressing them (moving near them). Buttons can be made shootable by giving them a health tag. Unless you want to have to shoot the button tons of times, set the health tag to "1". If you want to have the button flash when you shoot it, you must include all of the button animation textures in the level. You can just put them on brushes outside the level. 


------------------------------------------------------------------------


Quake is 1996 id Software. Some information about entities was obtained from the Unofficial Quake Specs, a truly awesome reference guide to Quake editing.

Disclaimer: This document is provided as is and may not be perfect. I do not guarentee the validity of any of the information in it. I will not be held liable or responsible for any damages caused from use or misuse of the information contained within this document.

